The invention relates to fuel cells and, more particularly, to improving detection of contaminants entering the fuel cell through the reactant streams and their subsequent removal from the system.
Poor reactant and water quality can adversely affect the performance of fuel cells. Fuel can frequently carry contaminants which may poison the catalyst of the fuel cell. Such contaminants include carbon monoxide, sulfur dioxide, hydrogen sulfide and the like. Foreign cations in the water, which is used to cool and humidify the fuel cell, can deposit in the cell and interfere with its proper operation. Foreign cations may also be introduced to the cell via the reactant streams, e.g. sodium chloride in air
Fortunately, fuel cells and especially PEM fuel cells have a demonstrated ability to recover from contamination. For example, catalyst poisons as discussed above can be removed, and catalyst activity recovered, by raising the anode potential to close to the air potential. This is accomplished in various methods including that which is disclosed in U.S. Pat. No. 6,841,278.
Foreign cations in the water can be removed through the water transfer plates, for example, by flushing the contaminated cells with clean water.
Although proper measures can be taken, nothing known in the art helps identify when such measures should be taken. Thus, such maintenance can to date only be done on a regularly scheduled basis, which clearly runs the risk of conducting such steps either when not needed or after performance of the fuel cell stack is already deteriorating, neither of which is desirable.
It is clear that the need exists for good indication as to when corrective or cleaning procedures based upon contaminants are needed.
It is therefore the primary object of the present invention to provide a system and method which identify when contaminants are present.
It is a further object of the invention to provide such identification in a system which is simple and reliable in practice, and which does not add significantly to the components or cost and/or weight of such components, of the fuel cell stack or power plant into which such measures are implemented.
Other objects and advantages of the present invention will appear below.